1. Field of the Invention
The present invention relates generally to a ventilation apparatus and a method for operating the same, and more particularly to a ventilation apparatus with feedback compensation control and a method for operating the same.
2. Description of Prior Art
A traditional home ventilation apparatus, such as an air interchanging fan, is usually involved a shaded-pole motor or a capacitor motor. Also, operation efficiency of the shaded-pole or capacitor ventilation apparatus is typically about 0.8 CFM/Watt to 5.0 CFM/Watt. Because the request of operation efficiency for Energy Star in US has to up to 2.8 CMF/Watt, a brushless DC motor (BLDCM) is now used most widely in the home ventilation apparatus.
BLDCM has the advantages, such as simple structure, ruggedness, free maintains, and small size, as well as the properties are similar to the DC motor. In addition, BLDCM is driven without exciting current because the rotor thereof is composed of permanent magnetic material to produce lower rotation inertia. Accordingly, BLDCMs are widely applied in precision machineries, automatic control applications, consumer electronics, and computer peripherals.
Although BLDCMs are used to significantly improve operation efficiency up to 6 CFM/Watt to 12 CFM/Watt, the maximum air flow thereof is reduced. Even if the air flow is increased, power consumption of the ventilation apparatus is correspondingly increased. Both the above-mentioned conditions can not conform to the requests for Energy Star in US.
Reference is made to FIG. 1 which is a circuit diagram of a prior art ventilation apparatus. The ventilation apparatus includes a power conversion unit 10A, a driven circuit 20A, a DC motor 30A, a current-sensing unit 40A, and a microcontroller 50A. The power conversion unit 10A receives an AC power voltage Vac and converts the AC power voltage Vac into a DC power voltage Vo. The power conversion unit 10A includes an electromagnetic interference filter 102A, a rectifier 104A, a pulse-width modulation integrated circuit (PWM IC) 106A, a DC converter 108A, a filter 110A, an optical coupler 112A, and an error amplifier 114A.
The electromagnetic interference filter 102A receives the AC power voltage Vac to eliminate noise of the AC power voltage Vac. The rectifier 104A is electrically connected to the electromagnetic interference filter 102A to rectify the filtered AC power voltage Vac and output a DC output voltage (not shown). The DC converter 108A is electrically connected to the rectifier 104 to receive the DC output voltage and convert energy provided from the AC power voltage Vac to a dc-side load. The filter 110A is electrically connected to the DC converter 108A to filter the DC voltage and produce the DC power voltage Vo. The PWM IC 106A is electrically connected to the rectifier 104A and the DC converter 108A to output a PWM signal and control power switches (not shown) of the DC converter 108A, thus providing an energy conversion between an input side and an output side of the power conversion unit 10A. The optical coupler 112A is electrically connected to the PWM IC 106A to provide signal isolation between the input side and the output side of the power conversion unit 10A. The error amplifier 114A is electrically connected to the optical coupler 112A to receive the DC power voltage Vo. The DC power voltage Vo is divided through the first resistor R1a, the second resistor R2a to obtain a divided voltage. The divided voltage is compared to a reference voltage V1 to produce an error amplifier signal (not shown) and the error amplifier signal is sent to the PWM IC 106A by the optical coupler 112A, thus controlling the DC converter 108A.
The driven circuit 20A is electrically connected to the power conversion unit 10A to receive the DC power voltage Vo and output a driven voltage (not shown), thus driving the DC motor 30A. The DC motor 30A is electrically connected to the driven circuit 20A and driven by the driven voltage outputted from the driven circuit 20A. In particular, the DC motor 30A is a brushless DC motor, BLDCM. The current-sensing unit 40A is electrically connected to driven circuit 20A and the DC motor 30A to sense an output current (not shown) outputted from the DC motor 30A. The microcontroller 50A is electrically connected to the current-sensing unit 40A and the driven circuit 20A to receive the output current and the DC power voltage Vo, thus controlling the driven circuit 20A to drive the DC motor 30A.
For controlling the ventilation apparatus by using voltage-dividing resistors, due to
  Vo  =      V    ⁢                  ⁢    1    ×                            R          ⁢                                          ⁢          1          ⁢          a                +                  R          ⁢                                          ⁢          2          ⁢          a                            R        ⁢                                  ⁢        2        ⁢        a            
Hence, the DC power voltage Vo is fixed when the first resistor R1a and the second resistor R2a are fixed, and the DC power voltage Vo is equal to
  Vo  =      V    ⁢                  ⁢    1    ×                            R          ⁢                                          ⁢          1          ⁢          a                +                  R          ⁢                                          ⁢          2          ⁢          a                            R        ⁢                                  ⁢        2        ⁢        a            
Reference is made to FIG. 2 which is a curve chart of air pressure and air flow of the prior art ventilation apparatus. FIG. 2 shows a first curve Cv1 (low-pressure and low-speed curve) and a second curve Cv2 (high-pressure and high-speed curve). When the ventilation apparatus is operated under the low-level DC power voltage Vo, the curve chart of air pressure and air flow of the ventilation apparatus is shown as the first curve Cv1. Similarly, the curve chart of air pressure and air flow of the ventilation apparatus is shown as the second curve Cv2 when the ventilation apparatus is operated under the high-level DC power voltage Vo.
Requests of power consumption and air flow for the ventilation apparatus are regulated by Energy Star in US as follows:                1. The energy efficiency needs to exceed 2.8 CFM/Watt based on 0.1 inch-H2O and 80 CFM; and        2. A ratio between air flow based on 0.25 inch-H2O and that based on 0.1 inch-H2O needs to exceed 60%.        
When the ventilation apparatus is operated along the first curve Cv1, the first request (energy efficiency) can be achieved. However, the second request cannot be achieved because a ratio between air flow based on 0.25 inch-H2O and that based on 0.1 inch-H2O is only 25% ( 20/80=25%) which is calculated by a first operation point Ps1 and a second operation point Ps2. Furthermore, the second request (air flow ratio which is calculated by a third operation point Ps3 and a fourth operation point Ps4) can be achieved when the ventilation apparatus is operated along the second curve CV2. However, the first request cannot be achieved because the air flow exceeds 80 CFM.
Hence, the ventilation apparatus is operated by only using voltage-dividing resistors cannot conform to the requests of Energy Star in US.
Accordingly, it is desirable to provide a ventilation apparatus with a feedback compensation control and a method for operating the same. The DC power voltage is compensated and regulated by a voltage compensation unit to conform to requests of power consumption and air flow for the ventilation apparatus.